S-4
The S-4 was designed by George Frye and introduced in 1968. The S4 sampling plug-in head provides one 50-ohm SMA input port with a 25ps risetime and a bandwidth of 14.5GHz. The unit provides a trigger pickoff signal for internal triggering and is specified for less than 5mV of noise. The S4 is the fastest of the S-series plug-in samplers. A interesting comparison of different sampling heads is found in "AN-3042a, Revision 1, 2/89".
The S4 sampling gate is based upon a traveling wave trapped-charge transmission line in which the sampling window is set by the propagation time of pulse edge through a thick-film transmission line. This technique requires only a sharp pulse edge rather than a precise pulse width, which is harder to generate. The sampling diodes are housed in a special coaxial connector that provides a high bandwidth signal path.
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Top view of the S4 plug-in
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Left view
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Right view
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Schematic
